This is a classic histologic example of a myxoid neurothekeoma, or nerve sheath myxoma. Clinically, they typically present on the head, neck, and upper extremities of middle age women, and therefore the location in this example is somewhat unusual. In difficult cases, the differential diagnosis may include cutaneous myxoma, mucus/myxoid cyst, myxoid neurofibroma, and mucinous adenocarcinoma. The lobular nature of this one is unmistakable. These lesions are usually S100 positive and GFAP positive, as in this case. They also stain with neuron specific enolase (NSE) and CD57. The cellular neurothekeomas are odd, expressing actin and only variably staining with neural markers.
At higher power, the nature of the spindle cells becomes more evident. These cells have bipolar or stellate cytoplasm. The nuclei are hyperchromatic and bland, with inconspicuous nucleoli. Mitotic figure are not present.